JPH02179266A - Solid-state power controller - Google Patents

Abstract

PURPOSE: To accelerate a response speed by lowering a voltage drop by providing a transistor and a current-detecting resistor between a power source and a load and controlling the switching of the transistor, in response to a load current value via a bias current source and a drive controller. CONSTITUTION: A transistor TrQ1 for turning current on and off and a current value detecting resistor RS are connected in series between a power source 28 and a load 30. When the TrQ1 is turned on, the current flows from the source 28 to the load 30. A signal that the resistor RS sends to leads 32, 34, is proportional to the load current is input to a drive controller 26 to turn on a TrQ3 , amplified by a differential/adding amplifier 22 via a bias current source 16. A bias current Ib is sent to diodes D1 , D2 reversely connected to a driver 14 via a DC-DC converter 24. The driver 14 has a Darlington connection of Trs Q2 , Q3 , and gives a sufficient base drive current to the TrQ1 , via a bias current which is proportional to a load current. Thus, an apparatus having small dissipation power and fast response speed is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrical switching devices and, more particularly, to solid state power controllers for use in DC circuits.

Relatively high voltage DC power distribution systems for use in new aircraft and space power systems are under development. These systems require solid-state power controllers for load and load bus control/protection to have capabilities that are difficult to achieve beyond the capabilities of current state-of-the-art switchgear, whether solid-state or electromechanical. ing. These power amplifiers must have low power consumption, low switch voltage drop, and the ability to perform current limiting actions quickly and accurately. In certain applications where the direction of the current can change at unpredictable times, it is necessary to control the current flowing between the load and the power source in two directions.

The present invention provides a highly efficient, reliable solid-state power controller with low voltage drop and rapid response.

A solid state power amplifier according to the invention includes an output circuit stage having a first transistor connected between a pair of output terminals. The collector of the transistor is connected to one end of a series circuit of two diodes forming part of a transistor drive circuit. A bias current source is connected to provide a DC bias current to the diode series circuit, and the drive circuit is also provided with means for connecting the other end of the diode series circuit to the base of the transistor.

In a second embodiment of the invention for use in a bidirectional power system, the output circuit stage includes a second ! A common connection point between the transistors includes a second transistor connected in series with the transistor of the output transistor and a second pair of diodes connected in reverse series with the branch connected in parallel to the two output transistors. connected to the common connection point between the diodes.

In both the uni-polar and bi-directional circuits described above, the output stage current is sensed and the DC bias current is adjusted to be proportional to the output stage current. Therefore, the response time becomes faster when current limiting operation is required.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a solid state power controller for use in a unipolar system, according to one embodiment of the present invention.

The power controller includes an output circuit stage with a transistor Ql having a main current conduction path between base and collector emitter, the collector of transistor Ql being connected to an output terminal lO
while the emitter of transistor Ql is connected to output terminal ! Connected to 2. Drive circuit! 4 includes a branch with a pair of series connected diodes D1 and D2, the first end of which is connected to the collector of transistor Q1. Bias current source 1B connects conductors 18 and 2
0 to supply a DC bias current to the series-connected diode D
A drive circuit voltage is generated across I and D2.

The bias current supply source 1B is connected to the differential summing amplifier 22 and the DC-
A DC converter 24 is included.

Darlington-connected transistors Q2 and QB act as a means of switching the voltage across diode O and D2 to the base of transistor Ql via diode O3, while diode D4 steers the current from the collector of transistor Q3 to the emitter of Ql. - The drive control circuit 2B, which acts as a diode and does not form part of the invention as it is constructed using known technology, supplies a proportional drive current to the base of the transistor Q3 to initiate conduction of the transistor Q1.

To explain the operation, when transistor Ql becomes conductive, current flows from external DC power supply 28 to external load 30. A resistive shunt Rg connected in series with the load generates a signal on conductors 32 and 34 that is proportional to the current in the output stage of the power controller. This current signal is applied to the conductor 3 along with the drive control circuit.
It is also sent to a differential summing amplifier which generates a DC voltage signal at B and 38. This DC voltage signal is proportional to the current in the output stage of the power controller.A DC-to-DC converter 24, constructed according to known techniques, converts the DC voltage signal on conductors 3B and 38 to an appropriate level on conductors 18 and 20. to ensure proper operation of the circuit.

The output transistor Ql is a power element that controls connection of the load to the power source and disconnection of the load from the power source. Drive circuit 14 is a power amplifier that interfaces drive control circuit 28 and the output stage. The drive circuit has series connected diodes 1 and D2 serving as an output voltage offset circuit supplied with a bias current rb from a DC bias source 1B.

The DC bias current Ib has a constant value or changes depending on the load current, as explained below.

The bias supply supplies forward bias current to diodes 01 and D2, which is connected to transistor Q1.
It needs to be of an appropriate size to supply sufficient base drive current.

One way to supply the base current is to determine the base current requirement at the rated load and supply a constant current of that magnitude whenever the output stage transistor is conducting. However, this method has the disadvantage that in most applications it introduces unnecessary losses in the drive circuit, given that the load current is lower than the rated current. An improved method is provided in which the magnitude of the current is proportional to the required value. To this end, a simple open loop control circuit is used to control the bias current source. The differential summing amplifier 22 shown in FIG.

Vout = Kl + K2 (1) where Vout is the output voltage on conductors 3B and 38, Kl and 2 are constants, and ■ is the load current flowing through the resistive shunt Rs. Designed with characteristics.

Due to this operating characteristic, the output voltage K is independent of the load current
l is given, the nonlinearity of the bias circuit is overcome, and a small bias current is obtained even at no load, and this bias current increases proportionally as the load current increases. In this manner, the power consumption of the drive circuit at no load is typically about 10 oz at full load, significantly improving the efficiency of the drive circuit.

In the circuit of FIG. 2, K1 is equal to the zener voltage of diode CRI times the ratio R3/R5; similarly, the quantity 2(1) is equal to Vin(R5/Rt).

When the circuit shown in FIG. 2 is used, the distortion of one circuit is reduced, reliability is improved, and the failure rate of circuit components is reduced. Furthermore,
FIG. 3 is a circuit diagram of a bidirectional power controller according to a second embodiment of the present invention, which can limit the fault current and improve the response time in the event of a fault by limiting the drive current. In the power controller of FIG. 3, output circuit stage 40 includes transistors Q5 and QB connected in series in a first branch including node 42.
has. A pair of reverse series connected diodes D7 and D8 are connected to the branch of S2 with node 44. The first and second branches are connected in parallel to each other between the output terminals 46 and 48, and the connection points of the first and second branches are connected to each other by a resistive shunt R''s. Stage 40 allows bidirectional current flow between circuit components 50 and 52, i.e. between circuit components 50 and 5.
2 is 0 that acts alternately as a power supply or load, for example,
If the circuit component 50 is a battery, it serves as a power source for feeding the rotary type 41152 that functions as a motor, and when the single-rotation type @52 functions as a generator, it serves as a power source for recharging the battery 50.

Drive circuit 54 includes Darlington connected PNP power transistors Q7 and QB. Although each of these transistors is shown as a single device, they are actually multiple parallel connected transistors. transistor Q
5. Qe, Q7. Q8 constitutes a complementary direct-coupled amplifier circuit. When current flows from terminal 4B to terminal 48, transistor Q[! , Q7. When QB conducts and current flows from terminal 48 to terminal 4B, transistor Q
5.Q7. QB conducts. Rectifier old, 02.03,
D4 provides base and steering current to output transistor Q5 or QB, which carries a current determined by the direction of the load current. Using these four rectifiers eliminates the need for two identical PNP drive circuits that are complex and degrade performance.

Diodes 05 and I]8 cooperate with the bias current [1111 as described in connection with FIG. 1 to provide a high operating potential to the drive circuit. By placing the resistive shunt in the appropriate position, a unipolar current indicating signal is generated which causes the bias source 18 to operate in both the unipolar and bidirectional power controller embodiments of the present invention. I can do it. QB and complementary P like QB
NP-NPN ) transistor circuit, NPN (Q
13) The voltage drop during conduction is at least PNP (QB
) equals the sum of the Vce of NPN (QEI) and the Vbe I) voltage drop, thus preventing transistor QB from operating in the low voltage drop saturation mode. Two rectifiers biased between the collector of QB and the emitter of QB
By adding 5 and 08, QB is biased to a level approximately 1.5 volts (DC) above the collector of QB. This is appropriately large enough to offset the undesired voltage component of the voltage drop when QB conducts. Therefore, transistor Q6 can operate in saturated conduction mode. When the current gain of the NPN transistor exceeds 10, the amount of power dissipated by the bias rectifier is significantly less than the power saved in transistor Q8, so that the net power reduction is reduced per ampere of collector current in QB. It becomes about 1.5 watts. This is very important since current designs are rated at 100 amps or more. The drive circuit of FIG. 3 has the advantage of limiting the fault peak current in the event of overload and load short circuits and limiting the base current of transistors Q5 and QB to improve response time.

150 amperes DC, 15G-
A circuit rated at 200 volts was constructed with a switch voltage drop of less than 2 volts DC at 150 amps. This efficient circuit design reduced controller losses to approximately 15 watts at 1% load and increased to 340 watts at 100% load. The current flowing during a short circuit was limited to a peak overshoot of less than 200 and a duration of 50 microseconds, thus limiting the power flow during a fault.

By providing a drive bias current that is proportional to the load current, the power controller of the present invention improves vehicle performance and reliability.

In a bidirectional power controller as shown in Figure 3, the voltage drop across the power switch is reduced by more than 33% compared to a conventional bidirectional device by incorporating an offset bias circuit in the drive stage. The use of a single driver circuit to drive both bidirectional output transistors simplifies the circuit, reduces the number of circuit components, and provides more efficient single-point power stage control. You will be able to do it.

Although the present invention has been described in terms of the presently preferred embodiment, it is likely that various modifications will occur to those skilled in the art without departing from the scope of the invention; It is to be understood that it is within the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a solid state power controller according to one embodiment of the present invention. FIG. 2 is a circuit diagram of the differential summing amplifier of the circuit of FIG. FIG. 3 is a circuit diagram of a second embodiment of the invention. 10.12 14 Fists ・ 16 ・ ・ 26 ・ Work 28 ・ 30 Hirobe (and 1 other person) FIG.

Claims (7)

[Claims] (1) an output circuit stage comprising a first transistor having a base and a first primary current conducting path between the collector and emitter, and means for connecting the collector to the first output terminal;
means for connecting the emitter to a second output terminal; a drive circuit comprising a pair of diodes connected in series in a first branch with a first end connected to the collector; a bias current source connected to supply a direct current bias current and means for generating a current signal proportional to the load current flowing through the output circuit stage, the drive circuit connected to the second end of the first branch; a bias current source responsive to the current signal to provide a direct current bias current proportional to the current signal. (2) The power controller according to claim 1, wherein the DC bias current has a predetermined minimum value. (3) The means for generating a current signal proportional to the load current flowing through the output circuit stage comprises a resistive shunt connected in series between the second output terminal and the load. The power controller according to item 1. (4) The bias current supply source includes a differential summing amplifier that receives a current signal and generates a DC voltage proportional to the current signal, and a DC voltage signal that receives a DC voltage signal and generates a DC bias current in the first branch. - The power controller according to claim 1, comprising a DC converter. (5) first and second branches connected in series with each other in a first branch, each having a base and a collector-emitter main current conducting path, the main current conducting path having a first connection point; an output circuit stage consisting of a transistor, a first pair of diodes connected in reverse series in a second branch with a second connection point, and a first pair of diodes connected at one end to the first connection point; a drive circuit comprising a second pair of diodes connected in series with each other in the third branch; a bias current source connected to supply a DC bias current to the third branch; the first and second branches are connected in parallel with each other between the pair of output terminals; , the drive circuit further includes means for connecting the other end of the third branch to the bases of the first and second transistors, and a bias current source is responsive to the current signal to convert the DC bias current into the current signal. A bidirectional power controller characterized in that it is proportional to . (6) The bidirectional power controller according to claim 5, wherein the DC bias current has a predetermined minimum value. (7) The bias current source includes a differential summing amplifier that receives the current signal and generates a DC voltage signal proportional to the current signal;
A bidirectional power controller comprising a DC-DC converter that receives a DC voltage signal and generates a DC bias current in a third branch.